The invention relates to a V-type internal combustion engine having two overhead camshafts per cylinder bank, which are driven from the crankshaft via a timing chain or a toothed belt and which actuate the inlet and outlet valves controlling the charge cycle of the internal combustion engine. The invention relates to a device for adjusting, relative to the engine crankshaft, the rotational-angle adjustment of the two camshafts actuating the inlet valves for an internal combustion engine.
The periodical "Sport Auto", 1986, No. 3, page 40 discloses an internal combustion engine of this general type. In this internal combustion engine, the two inlet and outlet camshafts are driven from the crankshaft via a single toothed belt. To enable a rotational-angle adjustment of the inlet camshafts relative to the crankshaft in this internal combustion engine, a separate camshaft adjuster would have to be arranged on each inlet camshaft. Both of those adjusters would have to be actuated in complete synchronism to enable identical displacement of the inlet valves of both cylinder banks to be realized. However, this would require a relatively complex control system. In addition, there are relatively large torque fluctuations in the cam drive in the case of a belt guide of this type.
It is known from German Offenlegeungsschrift 3,534,446 to couple two camshafts of an internal combustion engine to one another via a belt drive. Provided on this belt drive is a rotational-angle adjusting device with which a synchronous adjustment of the two camshafts relative to the crankshaft is possible. In this publication, however, nothing is stated about the belt guide in a V-type internal combustion engine.
The object of the instant invention is to create an internal combustion engine of the type described above, wherein an absolutely synchronous rotational-angle adjustment between the two inlet camshafts and the crankshaft can be achieved with minimum outlay and in which the torque fluctuations in the cam drive are reduced to a minimum.
The object is achieved according to the invention by having a rotational-angle adjusting device arranged on one of the two camshafts actuating the inlet valves of the internal combustion engine and with the two camshafts actuating the inlet valves coupled to one another via a further timing chain or a further toothed belt. The further timing chain or the further toothed belt provides an operative connection between output side of the rotational-angle adjusting device and the other camshaft actuating the inlet valves.
According to the invention, the inlet camshafts of the two cylinder banks are coupled to one another via a separate timing chain or a separate toothed belt. Here the two camshafts are driven by the timing chain, or the toothed belt, on the output side of a camshaft adjuster arranged on one of the two inlet camshafts. Thus an absolutely synchronous rotational-angle adjustment between the inlet camshafts of the two cylinder banks and the crankshaft can be achieved.
Furthermore, when the belt guide according to the invention is used, only one camshaft adjuster is necessary. By the direct connection between the two inlet camshafts via a separate timing chain, or a separate toothed belt, the fluctuations in the behavior of the cumulative torque of the inlet camshafts are reduced to such an extent that only a restraining torque acts on the camshaft adjuster in the lower speed range. In the case of a hydraulically actuable camshaft adjuster connected to an oil circuit dependent on engine speed, no rattling noises need therefore be expected in the area of the helical gearing of the camshaft adjuster when starting the internal combustion engine (where initially there is no oil pressure) and in the critical lower speed ranges in which the oil pressure is only minimal. These noises occur when a driving and a restraining torques act in constant alternation on the inlet camshafts. However, with the belt guide according to the invention, only restraining camshaft torques occur in these critical lower speed ranges and there is no longer any continual change in contact caused by clearance in the helical gearing of the camshaft adjuster. Rattling noises are thus eliminated. This advantageous behavior of the inlet camshaft torques exists in 8-cylinder internal combustion engines with a V-angle of 90.degree. and four valves per cylinder (two inlet and two outlet valves).
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.